WP0002 - FTTH Deployment Options for Telecom Operators

8/2/2019 WP0002 - FTTH Deployment Options for Telecom Operators

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AuthorsAuthorsAuthorsAuthors

Jani Saheb Shaik, N R Patil

AbstractAbstractAbstractAbstract

To realize the Government of Indias goal to have 20 millionbroadband subscribers by year 2010, it is essential to drive Fiber To

The Home (FTTH) technology along with other broadband access

technologies for providing broadband access. Today, majority of

broadband connectivity is offered through Digital Subscriber Line

(DSL), Cable Modem and to the limited extent with Wireless

technology. FTTH provides enormous bandwidth and long reach

offering Triple Play services (Data, Voice, Video) on a single fiber.

FTTH is future proof solution for providing add-on services such as

Video on demand, Online Gaming, HDTV. Advancement in the

electronic equipment coupled with falling prices of fiber and

equipment make FTTH deployment an affordable choice for the

telecom operators that result in long term returns. This paper details

various FTTH architectures available for deployment, key

developments and trends that are suitable for the current system

configurations.

Document: WP0002


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IntroductionIntroductionIntroductionIntroduction

Growing demand for high speed internet is the primary driver for the new access technologies

which enable experiencing true broadband. Traditionally telecom companies have been

offering T1 lines and DSL to small businesses, houses for applications such as voice services,high speed data, internet and video services. T1 lines are often expensive and DSLs

performance issues limit availability of these services. DSL Copper networks do not allow

sufficient data rates due to signal distortion and cross talk. Cable modem is another

competing technology for broadband services. In cable modems only few RF channels are

assigned for data and most of the bandwidth is dedicated to video channels.

FTTH offers triple play services with data speeds ranging from 155 Mbps to 2.5 Gbps Down

stream (Network to User) and 155 Mbps to 1 Gbps Up stream (User to Network) range of

services due to high bandwidth and though the field trials and technology development for

fiber in the access loop started in late 1980s, real deployments did not happen as the

deployment costs were very high at that time. In the last 20 years enormous progress is madein optical networking equipment and production of high quality optical fibers associated with

falling prices are driving forces for fiber to the home (FTTH).

The recent telecom bubble burst also had hard hit on the big telecom players and the revenue

generation from the long haul core networks are falling. This lead to shift in the business

strategy for maximizing the revenue generation from access loop and wireless. While there is

no standard definition for broadband, definition of broadband has become country specific. In

Japan more than 1 Mbps is defined as broadband and in India bandwidth more than 256 Kbps

is specified as broadband.

Table 1 shows some potential future residential applications and their bandwidth

requirements.

Table 1

Application Bandwidth (Mbps)

1 High Definition Video Session 20

2 Standard IP Video Session 7

1 Web Surfing Session 1

Internet Appliances 1

1 Internet Gaming Session 2

2 Video Conferencing Sessions 2

4 High Quality Audio Sessions 0.5

Total 33.5

FTTH ArchitectureFTTH ArchitectureFTTH ArchitectureFTTH Architecture

Active and passive are two commonly used FTTH architectures fro FTTH deployment. Active

Architecture is also called as Point 2 Point (P2P) and Passive Optical Network (PON) architecture

is called Point to Multi Point (P2M). Choice of active or passive architectures for deployment


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depends on the type of services to be delivered, cost of the infrastructure, current infrastructure

and future plans for migrating to the new technologies.

ACTIVE TechnologyACTIVE TechnologyACTIVE TechnologyACTIVE Technology

Active Ethernet also called Ethernet Switched Optical Network (ESON) or Point to Point (P2P)Network Architecture provides a dedicated fiber to the side from the central office exchange

shown in the figure 1. A P2P architecture is a very simple network design.

Figure 1

Since the fiber is dedicated, operation, administration and maintenance of the content and

trouble shooting become easy. Active FTTH solutions are implemented in many different ways

through both standard and proprietary methods.

Since the distances of the central node an remote sites are known, estimation of power

budget, trouble shooting the faults in the network would be easier. Transmission in P2P

configuration, is more secure, since all transmissions are physically separated by fiber.

Only the end points will transmit and receive information, which is not mixed with that of any

other customer.

Active Network Architecture and ComponentsActive Network Architecture and ComponentsActive Network Architecture and ComponentsActive Network Architecture and Components

Core switch, aggregation switch and Optical Network Terminal (ONT) are main building blocks of

a P2P network. The core switch is a high capacity Ethernet switch that communicates to

aggregator switches using standard GbE optical signals. The aggregator switch interfaces this

data stream to multiple Premises Gateways called Optical Network Terminals (ONT). Each ONT

interfaces a 100 Mb/s signal in a standard 100 BaseFX format, which is 100 BaseT Ethernetformat on an optical fiber. The core switch interfaces multiple content and service providers over

an MPLS-based Metro or Regional network to deliver data, video, and voice services to the users

on the access network.

Aggregator switch resides in both standard CO and in building entrance and in outside plant

cabinets to meet the environmental needs of the network provider. The aggregator switch

delivers traffic to the subscriber in accordance with the specific bandwidth requirements from 1

Mb/s to 100 Mb/s (symmetrical) per subscriber. A typical connectivity diagram of Active

technology in the access network is shown if figure 2.


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Figure 2

PON TechnologyPON TechnologyPON TechnologyPON Technology

PON is a point to multipoint (P2M) network. Each customer is connected into the optica

network via a passive optical splitter, therefore, no active electronics in the distribution

network and bandwidth is shared from the feeder to the drop. The advantage of FTTH PON is

the fact that they use purely optical passive components that can withstand severe and

demanding outside plant environment conditions without the need to consumer energy

between in the central office exchange and the customer premises. The benefit to telecom

operators is that low maintenance requirements of these passive optical components will


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significantly reduce of the cost of upgrades and operating expenditures. Passive systems

utilize a common shared connection with the centralized electronics. PON architecture uses

unidirectional splitters. PON FTTH solutions are driven by two key standards:FSAN/ITU and

EFMA/IEEE, and solutions can be built with either standard. The PON architecture can reduce

the cable cost as it enables sharing of each fiber by many users. There are different PONtechnologies available today.

Typical PON architecture is shown below, Figure 3.

Figure 3

Deployment of active technology is picking up with many municipalities in USA (Utopia, iProvo)

offering services over the active P2P technology and is competing with PON technology. Table-

2, details the similarities and differences of active and PON architectures.

Table 2

Parameter ACTIVE

(Point to Point / P2P)

PASSIVE OPTICAL NETWORKS

(Point to Multi Point / P2M)

TopologyTopologyTopologyTopology

Ethernet Switched Optical Networks (ESONs)

contain an active electronic element, a switch

aggregator, between the central office (CO) or

head-end switch and the Customer Premise

Equipment (CPE).

Passive Optical Networks (PONs) do not

contain any electronics between the CO

switch and the CPE. In a PON, the active

optoelectronics are situated on either ends

of the passive network.

StandardsStandardsStandardsStandards

It is based on IEEE 802.3 standard. The recent

completion of the 10 Gigabit Ethernet

standards (802.3ae) provides a seamless

transition from 1 Gigabit to 10 Gigabits.

There are three main varieties of PON today.

APON/BPON: ITU-T G.983, EPON: IEEE

802.3ah, GPON: ITU-T G.984

NetworksNetworksNetworksNetworks

SupportedSupportedSupportedSupportedIP IP, ATM, TDM

No. of HomesNo. of HomesNo. of HomesNo. of Homes

ServedServedServedServed

ESON systems can serve up to 48 homes, on

each fiber run, and isolate information streams

and faults to each subscriber. As more homes

are served additional bandwidth is added and

up to 50,000 homes can be served from asingle core switch centrally located.

Conserves fiber resources. It uses a

technique called power splitting and can

only serve 32 homes from one fiber run with

BPON and EPON. 64 homes with GPONtechnology.

BandwidthBandwidthBandwidthBandwidth

Only the content destined for a particular CPE is

delivered to that subscriber. Even if a rogue CPE

device is installed in an active network, no

content is delivered to it.

In a PON the entire downstream bandwidth

is transmitted to the power splitter, and a

portion of the optical power is delivered to

each subscriber. Since bandwidth in a

passive system is not dedicated to each

subscriber, each user shares the total

capacity of the system.

ContentContentContentContent

DistributionDistributionDistributionDistribution

and backhauland backhauland backhauland backhaul

Video stream is launched from the core switch

to the aggregation switch when a service is

ordered. If multiple subscribers order the same

All subscribers are exposed to all

downstream content, however, the OLT

communicates with valid ONT only by


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bandwidthbandwidthbandwidthbandwidth

utilizationutilizationutilizationutilization

service, it is electrically split at the aggregation

switch and delivered to the second subscriber

and only to the second subscriber. Thus,

backhaul bandwidth is more efficiently used

and content is not delivered to unintended CPE

devices.

verifying the password. When a subscriber

orders a video service of 5 Mbps, for

example, a separate information stream is

launched from the OLT to each subscriber.

Therefore, 10 orders for the same content

spawn 10 streams of 5 Mbps down to allsubscribers.

RangeRangeRangeRange

Ethernet to the Subscriber platforms can be

located up to 120 km from each other without

any geographic restrictions, or variations in the

platforms. Active Ethernet use standard-based

Small Form Factor Pluggable (SFP) optical

transceivers.

Two main factors restrict the total reach of

PON deployments. The first is the total

available optical power budget, which is a

factor of the OLT laser port and the total loss

budget, including the fiber feeder and

splitters. Secondly, because ONUs share the

optical feeder and OLT port, a sophisticated

algorithm is required within all the devices to

prevent more than one ONU from

transmitting at the same time, which would

cause traffic collisions rendering

applications like video unusable. APON and

EPON are limited to a maximum of 20 Km

between the OLT and the ONU.

ScalabilityScalabilityScalabilityScalability

ESONs can be initially provisioned to deliver 20

Mbps to each subscriber and later remotely

upgraded to 100 Mbps.

PONs must physically restrict the number of

subscribers on a power splitter to achieve

higher throughputs. If the total network

capacity is exhausted, then the electronics at

each end (CO and CPE) must be upgraded to

a newer technology.

APON / BPONAPON / BPONAPON / BPONAPON / BPON

ATM Passive Optical Network:ATM Passive Optical Network:ATM Passive Optical Network:ATM Passive Optical Network: APON was initiated in 1995 by ITU/FSAN andstandardized as ITU-T G.983. In 1999, ITU adopted FSANs APON standard. APON was the firstPON based technology developed for FTTH deployment as most of the legacy network

infrastructure was ATM based. There are different PON technologies available today. Since the

services offered by this architecture are not only the ATM based serviced but also video

distribution, leased line services and Ethernet access and to express the broadband capability

of PON systems APON is renamed as BPON. Broadband Passive Optical Network (BPON) was

standardized by ITU recommendations G.983.1, G.983.2, G.983.3. BPON has two key

advantages, first it provides 3rd wavelength for video services, second it is stable standard that

re-uses ATM infrastructure. ITU-T recommendation G.983.1 defines three clauses of

performance namely Class A, Class B, Class C.

GPONGPONGPONGPON

The progress in the technology, the need for larger bandwidths and the complexity of ATM

forced the FSAN group to look for better technology. Gigabit Passive Optical Network (GPON)

standardization work was initiated by FSAN in the year 2001 for designing networks over

1Gbps. GPON architecture offers converged data and voice services at upto 2.5 Gbps. GPON

enables transport of multiple services in their native format, specifically TDM and data. In

order to enable easy transition from BPON to GPON, many functions of BPON are reused for

GPON. In January 2003, the GPON standards were ratified by ITU-T and are known as ITU-T


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Recommendations G.984.1, G.984.2 and G.984.3. The GPONs uses Generic Framing

Procedure (GFP) protocol to provide support for both voice and data oriented services. A big

advantage of GPON over other schemes is that interfaces to all the main services are provided

and in GFP enabled networks packets belonging to different protocols can be transmitted in

their native formats.

EPONEPONEPONEPON

Ethernet equipment vendors formed Ethernet in the First Mile Alliance (EFMA) to work on a

architecture for FTTH as Ethernet is a dominant protocol in Local Area Network. EPON based

FTTH was adopted by IEEE standard IEEE 802.3ah in September 2004.

Adopting Ethernet technology in the access network would make uniform protocol at the

customer end simplifying the network management. Single protocol in Local Area Network

Access Network and Backbone Network enables easy rollout of FTTH. EPON standards

networking community renamed the term last mile to first mile to symbolize the importanceand significance access part of the network. EFM introduced the concept of Ethernet Passive

Optical Networks (EPONs), in which a point to multipoint (P2MP) network topology is

implemented with passive optical splitters. EPON, is largely vendor-driven standard and it is

fundamentally similar to ATM-PON but transports Ethernet frames/packets instead of ATM

cells. It specified minimum standardization and product differentiation, also it has decided not

to standardize the Bandwidth Allocation Algorithm (DBA), TDM and ATM support, Security

Authentication, WDM Overlay Plan, support for Analog Video Protection, Diagnostics

Monitoring, Compliance with existing OSS leaving these to the vendors to choose the best.

WDM PONWDM PONWDM PONWDM PON

Wavelength Division Multiplexing Passive Optical Network (WDM PON) is the next generation in

development of access networks and offer highest bandwidth. Though it will be some time

before there are affordable WDM PONs some vendors are introducing products that can put

more wavelengths onto a PON. Wavelength Division Multiplexing (WDM) is either a Coarse

(CWDM) or Dense (DWDM) depending on the number of wavelengths multiplexed onto the same

fiber. Vendors are of the opinion that a CWDM PON can support 3 to 5 wavelengths, while

supporting more than 5 wavelengths requires a DWDM overlay. In WDM PON architecture ONTs

operate on different wavelengths and hence higher transmission rates can be achieved. Much

research was focused on enhancing WDM PONs ability to serve larger numbers of customers in

attempt to increase revenue from invested resources. As a result, some hybrid structures have

been proposed where both WDMA and TDMA modes are used to increase the number ofpotential users. For DWDM, the ONTs require expensive, frequency-stable, temperature

controlled lasers. The OLT puts all the wavelengths onto the shared feeder fiber and the splitters

replicate the wavelengths to each home.

PON Architecture and ComponentsPON Architecture and ComponentsPON Architecture and ComponentsPON Architecture and ComponentsThe Optical Line Terminal (OLT) is the main element of the network and it is usually placed in the

Local Exchange and its the engine that drives FTTH system. Optical Network Terminals (ONTs)

are deployed at customers premises. ONTs are connected to the OLT by means of optical fiber

and no active elements are present in the link. A single ONT can serve as point of access for one


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(Fiber to the Home) or multiple (Fiber to the Block or Curb) customers and be deployed either at

customers premises (Fiber to the Home or Block) or on the street in a cabinet (Fiber to the

Curb).

Splitters in outside plant are important in signal distribution. The ITU G.983.1 standardrecommends splitting the signal up to 32 users. The final splitting ratio can be achieved using a

single splitter device, a single 1X32 splitter or a cascaded series, such as 1X8 + 1X4 or 1X16 +

1X2. To split the incoming signal from the Central Office to subscribers, the passive optical

splitter need to have the following characteristics:

Broad operating wavelength range Low insertion loss and uniformity in any conditions Minimal dimensions High reliability Support network survivability and protection policy

In PON the transceiver in the ONT is the physical connection between the customer premises

and the central office OLT. WDM triplexer module separates the three wavelengths 1310 nm

1490 nm and 1550 nm. ONT receives data at 1490 nm and sends burst traffic at 1310 nm.

Analogue video at 1550 nm is received. Media Access Controller (MAC) controls the upstream

burst mode traffic in an orderly manner and ensures that no collision occur due to upstream

data transmission from different homes. Video receiver circuitry converts the 1550 nm

downstream analogue signal to 75 ohm co-axial signal. The Customer Premises Equipment

(CPE), also known as the Optical Network Unit (ONU), has POTS (Plain Old Telephone Service)

10/100 Base-T Ethernet and RF video interfaces. Figure 4 shows the typical PON architecture

connectivity.

Figure 4


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Video DeliveryVideo DeliveryVideo DeliveryVideo Delivery

Video in FTTH network can be delivered as either video over IP or RF overlay. Video over IP has

definite advantages over RF overlay but requires a set top box interface to connect to TV sets.

Today, many carriers are offering data services over IP protocol. Delivery of video over IP willmake integration and managing the service easy. Video over IP enables interactivity between

content provider and the subscriber. The ITU-T G.983.3 specifies an Enhancement Band (EB) of

between 1539 nm and 1565 nm which allows the use of wavelengths in addition to those

specified in G.983.1. Schematic of RF overlay is shown figure 5. RF overlay overcomes the

bandwidth limitations of the network but has limitations on interactivity. It is not easy to

provide Rf return path in RF overlay. ONTs with RF interface enables the customer to directly

plug the TV sets without need for a set top box. The main blocks in BPON network with RF

overlay are depicted in figure 5. At the Central Office (CO), video is coupled from the head-end

into the optical distribution network (ODN) via a WDM filter or a 2XN coupler. The head-end

consists of a continuous wave laser diode at 1550 nm, and the signal is passed through an

erbium doped-fiber amplifier (EDFA) fro increasing the optical power. At the ONT, the videosignal is optically demultiplexed. Both analog and digitally modulated channels can be viewed

(the latter with a set-top box). The up- and downstream data paths are carried in different

wavelength bands (respectively in 1260-1360 nm and 1480-1500 nm), and are also

separated by WDM filters. Figure 5 shows typical architecture of video over RF overlay.

Figure 5


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CableCableCableCable Segments in FTTH NetworkSegments in FTTH NetworkSegments in FTTH NetworkSegments in FTTH Network

Access network Out Side Plant (OSP) cabling can be categorized into three segments, namely

Feeder cables, Distribution cables and Drop cables. Figure 6 illustrates cable configurations.

Feeder and Distribution CablesFeeder and Distribution CablesFeeder and Distribution CablesFeeder and Distribution Cables

Optical fiber cables running from central office exchange to the Local Convergence Point (LCP)

are termed as feeder cables. Distribution cables start from LCP and run to the entrance of the

neighborhood. A single feeder cable serves several distribution cables loose tube design

cables are most popular in feeder and distribution segments of access network. Loose design

cables offer several benefits stress free movement of fibers under varying environmenta

and mechanical conditions. Midspan access for branching out the fibers can be conveniently

done with loose tube cables.

Drop CablesDrop CablesDrop CablesDrop Cables

The portion of the cable connecting Network Access Point (NAP) to the subscriber premises is

called as drop cable. Usually drop cables have less fiber count and length ranges upto 100

mts. Drop cables are designed with attributes such as flexibility, less weight, smaller diameter,

ease of fiber access and termination. Typical drop cable cross section, used for aeria

applications, is shown in figure 6.

Figure 6

In non-aerial applications, the following type of flat drop cable is used, figure 7.

Figure 7


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World Wide FTTH Deployments

JapanJapanJapanJapan

Japan has the largest and most successful fiber-to-the-home (FTTH) deployments in the world

till date. The Japanese Ministry of Public Management estimates that by Marhc 2006 there

will be 7.73 million households connected to the Internet by means of the optical fiber in

Japan. While the Japanese carriers have initially adopted ATM based BPON architecture and

the growing demand for higher bandwidth has forced them to look for alternative option. Now

Japanese carriers have started embracing EPON solution also called as GE-PON.

USAUSAUSAUSA

In US, majority of the carriers are launching FTTH services with BPON architecture. With the

development and availability of GPON, many of the carriers have planned for migration toGPON architecture.

KoreaKoreaKoreaKorea

In Korea, 74% of the population already has a broadband connection to the Internet and main

telecommunications companies are investing heavily in the optical infrastructure in order to

maintain their competitive edge.

EuropeEuropeEuropeEurope

In Europe broadband access is getting more and more attention. The eEurope 2005 programwas launched by the European Council in 2002. Its agenda is primarily concerned with

promoting broadband Internet in member countries.

ChinaChinaChinaChina

In recent years China has been catching up with the leaders. Chinese telecommunication

carriers are still at the stage of testing and promoting FTTH without actual commercia

applications. Throughout the promotion stage, FTTx, as just one of several broadband access

technologies, has faced fierce competition from xDSL. In 2004, a more complete FTTH

demonstration project was undertaken in order to verify FTTH technology and product

maturity, and serve as the foundation for future FTTH applications. In particular, the OpticsValley of China in Wuhan city is a nearly complete demonstration of an FTTH testing point.

IndiaIndiaIndiaIndia

Ministry of Communications & Information technology has recognized the need to increase the

broadband penetration in the country. Broadband policy-2004 puts FTTH as the one of the

major broadband options. Many carriers have already deployed fiber to the curb. Finalization

of FTTH drop cable specifications by TEC is the first step in this direction. Private and public


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telecom operators are already in the process of conducting trials on broadband on FTTH

network.

ConclusionOne of the major hurdles for the mass deployment of FTTH is the relatively high cost of

CPE/ONT. Equipment vendors efforts to integrate various functions into a single IC would bring

down the cost of ONTs. Carriers have a large installed base of TDM based legacy infrastructure

There is no right or wrong FTTH technology, rather the technology choice primarily depends on

the existing network operator infrastructure. With ambitious plans of Govt. of India to increase

the broadband availability, making a parallel start of FTTH would only make achieve the

targets set by the Govt. Both the architectures of FTTH: P2P and P2MP offer scalability and

flexibility for FTTH, though ultimately, the choice of network architecture is typically driven by

the demand for that which offers the greatest service capabilities at the lowest costs.

Glossary of TermsAPON: ATM Passive Optical Network

ATM: Asynchronous Transfer Mode

BPON: Broadband Passive Optical Network

EPON: Ethernet Passive Optical Network

GPON: Gigabit Passive Optical Network

IEEE: Institute of Electrical and Electronics Engineers

OLT: Optical Line Terminal

ONT: Optical Network Terminal

ITU: International Telecommunications Union

EFM Ethernet in First Mile

EFMA Ethernet in First Mile Alliance

FSAN: Full Services Access Network

ESON: Ethernet Switched Optical Network

References:1. Broadband optical access systems based on Passive Optical Networks (PON), ITU-T

G.983.1

2. Optical Access Networks to support services up to The ISDN Primary rate or equivalentbit rates ITU-T G.983.2

3. A broadband optical access system with increased service capability by wavelengthallocation, ITU-T G.983.3

4. Gigabit capable Passive Optical Networks (GPON): General characteristics5. FTTP deployments in the United States and Japan-Equipment Choices and Service

provider Imperatives, Journal of Lightwave Technology, Vol.23, No.1 Jan 2005, Mark

Abrams, Philippe C.Becker, Y.Fujimoto, Vincent OByne, David Piehler

6. Past-Present-Future of Fiber to the Home Solutions, Joseph Kim, Ph.D7. Comparing Gigabit PON Technologies, Flexilight Networks8. Design and Analysis of PON, Glen Kramer and Biswanath Mukherjee, University of

California

9. Video over BPON with Integrated VDSL, lan Cooper, Vince Barker, Martin AndrewsMick Bramhall, Peter Ball


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10.WDM-upgraded PONs for FTTH and FTTBusiness, C. Bouchat, C. Dessauvages, FFredricx, C. Hardalov, R. Schoop, P. Vetter

11.Fiber-To-The-Premise Network Architecture: Design Aspects of PON Optical AccessNetworks, Patrick J. Sims

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WP0002 - FTTH Deployment Options for Telecom Operators